The invention relates generally to semiconductor manufacturing equipment and, more particularly, to wafer transfer machines.
Generally, semiconductor devices are mass produced by forming many identical circuit patterns on a single silicon wafer which is thereafter cut into many identical dies or xe2x80x9cchips.xe2x80x9d Semiconductor devices, also commonly referred to as integrated circuits, are typically constructed by successively depositing or xe2x80x9cstackingxe2x80x9d layers of various materials on the wafer. Each layer is patterned as necessary to form the desired circuit components. To ensure reliable and predictable operation of integrated circuits, the wafer and deposited materials must be free from contamination. Hence, many fabrication processes must be performed in an environment that is essentially free from contamination. For example, the contamination level requirement for Class 1 cleanliness in semiconductor wafer processing areas or xe2x80x9cclean roomsxe2x80x9d is less than one part (contaminates) per cubic foot. To achieve this high degree of cleanliness, special high volume ventilation systems are used to continuously filter the air. These systems represent a significant contribution to the overall cost of manufacturing semiconductor devices. Accordingly, substantial cost savings can be realized by minimizing the size of the clean rooms and by making the most efficient use of all available clean room space.
A number of different size wafers, ranging from 3 inches in diameter to 8 inches in diameter, are currently produced in the semiconductor industry. In addition, development efforts are underway to produce 10 and 12 inch diameter wafers. While it is economically desirable to have the capability to produce wafers of all sizes, each size wafer generally requires its own special processing equipment. The redundancy in equipment to process different size wafers increases equipment costs as well as the size of the clean room and the associated construction and maintenance costs. Cost and space savings could be realized if the same equipment could be used to process different size wafers.
During the manufacture of semiconductor devices, the wafers are subjected to a number of different processes and environmental conditions. Wafer carriers, sometimes also called cassettes or xe2x80x9cboats,xe2x80x9d are used to house the wafers for bulk storing and transporting through the manufacturing processes. Wafer carriers are not typically suitable for exposure to all of the different environmental conditions encountered during processing. As a result, the wafers have to be transferred between boats at various times during the production of the semiconductor devices. Wafer transfer machines are used to perform this task. Wafer transfer machines generally consist of a base and a transfer arm. A first carrier containing wafers and a second empty carrier are placed in fixed opposing positions on the base. The transfer arm is operable to move the wafers from the first carrier to the second carrier. Conventional wafer transfer machines are capable of transferring only one size wafer. A different machine must be acquired and placed in the clean room for each different size wafer and associated wafer carriers.
The present invention is directed to a wafer transfer machine that is capable of transferring different size wafers between their respective wafer carriers. It is one object of the invention to provide a readily convertible wafer transfer machine that can be used to perform wafer transfer operations for different size wafers. It is another object to reduce the number of machines necessary to support the processing of different size wafers, particularly in a clean room environment. It is a further object of the invention to reduce the equipment and associated clean room costs for the manufacture of semiconductor devices.
According to the present invention, these and other objects and advantages are achieved by a semiconductor wafer transfer machine for transferring first wafers having a first diameter from a first transferor carrier to a first receiver carrier and second wafers having a second diameter different from the first diameter from a second transferor carrier to a second receiver carrier. The wafer transfer machine includes a base plate with a longitudinal axis for placement on the base plate of the transferor carriers and the receiver carriers and a mechanism for transferring wafers contained in the first and second transferor carriers to the first and second receiver carriers, respectively. The wafer transfer machine also includes an adjustable positioner that comprises (1) a transferor positioning mechanism for aligning the first and second transferor carriers on the top surface of the base plate, (2) a first receiver positioning mechanism for aligning the first receiver carrier in a first position with respect to the first transferor carrier on the top surface of the base plate, and (3) a second receiver positioning mechanism for aligning the second receiver carrier in a second position with respect to the second transferor carrier on the top surface of the base plate.
In one preferred version of the invention, the transferor positioning mechanism includes a transferor axial positioning mechanism for aligning the first and second transferor carriers along the longitudinal axis of the base plate, the first receiver positioning mechanism includes a first receiver axial positioning means for aligning the first receiver carrier along the longitudinal axis of the base plate, and the second receiver positioning mechanism includes a second receiver axial positioning mechanism for aligning the second receiver carrier along the longitudinal axis. The transferor positioning mechanism preferably also includes a transferor transverse positioning mechanism for aligning the first and second transferor carriers laterally with respect to the longitudinal axis of the base plate. The first receiver positioning mechanism preferably also includes a first receiver transverse positioning mechanism for aligning the first receiver carrier laterally with respect to the longitudinal axis of the base plate. Similarly, the second receiver positioning mechanism also preferably includes a second receiver transverse positioning mechanism for aligning the second receiver carrier laterally with respect to the longitudinal axis of the base plate.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.